1. Field of the Invention
This invention relates to automated window shading systems, specifically systems having the object of automatically anticipating a user's shading preferences under changing conditions, and of automatically adjusting the shading according to those preferences.
2. Discussion of Prior Art
Automated Shading Systems
In this disclosure, I use the term inconvenience to refer to the sensory, cognitive, and physical efforts associated with human tasks. Because inconvenience has an important and special meaning in the context of my invention, I use italicized text to refer to it throughout this disclosure (as well as to other terms and phrases with special meanings in the context of my invention).
There is great demand for systems directed toward reducing inconvenience. For purposes of this disclosure, I make a distinction between two types of such system: mechanized systems and automated systems.                Mechanized systems reduce just the physical effort associated with a given task.        Automated systems reduce the cognitive and sensory efforts, as well as the physical effort, associated with a given task.        
An important class of automated system is one that attempts to anticipate or emulate human behavior. For example, an object of an automated window-shading system is to anticipate a user's shading preferences under changing conditions, and to automatically adjust the shading according to those preferences—thus sparing the user the cognitive and sensory (as well as physical) efforts associated with making deliberate shading adjustments.
Of course, no automated shading system can fully anticipate the desires of its user, so occasional deliberate shading adjustments will still be necessary. One metric of the effectiveness of such a system is the degree to which it reduces the frequency of required deliberate adjustments. Another important consideration is the effort required to “teach” the system the user's preferences so that it “knows” when and how to adjust the shading.
Thus, an ideal automated shading device would be one that (1) substantially reduces the frequency of required deliberate shading adjustments, and (2) is simple and easy to “teach”. Another way of stating this object is that an ideal automated shading device should virtually eliminate the inconvenience associated with window shading—both the short-term inconvenience associated with teaching or programming the system, as well as the long-term inconvenience associated with the need to make deliberate shading adjustments.
Unfortunately, conventional automated shading technology falls far short of this ideal, and instead forces a trade-off between short-term inconvenience and long-term inconvenience:                My research shows that conventional automated shading devices that do not require a complex, inconvenient teaching process (and thereby minimize short-term inconvenience) do not substantially reduce long-term inconvenience.        Conversely, conventional automated shading devices that do reduce long-term inconvenience typically require a complex and inconvenient teaching process, thus resulting in significant short-term inconvenience. Moreover, such systems do not reduce long-term inconvenience enough to justify their purchase by mainstream buyers.FIG. 1: Inconvenience Associated with Conventional Mechanized Shading Devices        
A useful reference point for assessing the inconvenience associated with use of various automated shading devices is the inconvenience associated with use of a mechanized (but non-automated) shading device. Such a device typically uses an electric motor to actuate an adjustable window covering, thereby eliminating much of the physical effort associated with shading adjustments. However, the user must still deliberately initiate every shading adjustment (typically via a remote control), which requires some cognitive, sensory, and physical effort. I use this level of effort as the reference level in discussing the requirements for, and effectiveness of, various automated shading devices.
FIG. 1 is a plot of the relative inconvenience versus time associated with the use of a conventional mechanized shading device. The relative inconvenience is a function of the average frequency of required deliberate adjustments, which in turn depends on factors such as climate and user preferences. However, for the purposes of this discussion, this average frequency may be considered effectively constant. Thus, as shown, the inconvenience is also constant with time, and represents the reference level of inconvenience for purposes of this disclosure.
Categorization of Prior-Art Automated Shading Systems
Conventional automated shading systems can be broadly grouped into three categories:                Sensor-based discrete-control systems automatically adjust the shading to discrete, predetermined settings under predetermined conditions.        Sensor-based continuous-control systems automatically adjust the shading across a continuum of settings as a function of at least one sensed variable.        Clock-based systems automatically adjust the shading to predetermined settings at predetermined times.Sensor-Based Discrete-Control Systems        
A sensor-based discrete-control system adjusts the shading to predetermined settings as a function of the prevailing environmental condition. The environmental condition is a discrete variable representing a combination of one or more discrete variables, each of which has a value that depends on the output of a sensor (e.g., a photocell) relative to one or more predetermined thresholds.
Simple Sensor-Based Discrete Control Systems
For example, a simple system might have a single sensor (e.g., an outward-facing photocell) and use a single threshold (e.g., a threshold representing the brightness at dusk or dawn) to determine the value of a single discrete, binary variable (e.g., representing daytime/nighttime). In such a system, the discrete environmental condition variable has only two possible values (e.g., “daytime” or “nighttime”), and there are only two corresponding predetermined shading settings. When the sensor output crosses the threshold, the shading is automatically adjusted to the setting corresponding to the new environmental condition.
An early example of such a single-sensor system is the automatic shade disclosed in U.S. Pat. No. 2,149,481 to Bosch et al (1939). Bosch et al disclose an embodiment responsive to temperature (as sensed by a thermostat), as well as an embodiment responsive to light level (as sensed by a photocell).
FIG. 2: Inconvenience Associated with Simple Sensor-Based Discrete Control System
FIG. 2 shows a plot of estimated inconvenience versus time for a simple sensor-based discrete-control automated shading system capable of only dusk/dawn operation, as described above.
Before use, such systems must be taught, or programmed with, the desired dusk and dawn settings. As shown in FIG. 2, this programming step represents only slightly greater inconvenience than the reference level, and can be completed quickly. However, after programming, such systems do not significantly reduce the inconvenience below the reference level. This is because people generally do not make shading adjustments on the basis of just a single environmental variable (e.g., brightness), so such systems are incapable of effectively anticipating human shading preferences under changing conditions.
Thus, while such systems do not cause excessive short-term inconvenience, neither do they significantly reduce the long-term inconvenience associated with shading adjustments.
Complex Sensor-Based Discrete-Control Systems
Also known in the art are sensor-based discrete-control systems with multiple sensors. Such a system might include, for example, an outward-sensing photocell and an inward-facing Passive InfraRed (PIR) occupancy sensor. These sensor outputs would be compared to appropriate thresholds to obtain the values of a daytime/nighttime binary variable and an occupied/unoccupied binary variable, respectively. These two binary variables, in turn, would define four unique environmental conditions, each of which would be associated with a predetermined shading setting. Such a system would automatically adjust the shading to the corresponding predetermined setting when the output of either sensor crosses the corresponding threshold. Examples of multiple-sensor systems include:                The system disclosed in U.S. Pat. No. 3,675,023 to Kunke et al. (1972). This system includes a light sensor and a heat sensor, with associated control elements, to control the operation of a motorized Venetian blind. The system automatically closes the blind when the outputs of either the light sensor or heat sensor exceed predetermined thresholds, and automatically opens the blind when the outputs of both the light sensor and heat sensor are below predetermined thresholds.        The IntelliFlex® motorized-shade control system with optional Sun-Sensor, manufactured by Draper, Inc. of Spiceland, Ind., which includes optional sun and wind sensors.FIG. 3: Inconvenience Associated with Complex Sensor-Based Discrete Control System        
FIG. 3 shows a plot of estimated inconvenience versus time for a sensor-based discrete-control automated shading system using both dusk/dawn and occupancy sensors.
Some such multi-sensor systems are, indeed, capable of providing a noticeable (but still modest) reduction in the frequency of required deliberate shading adjustments and, thus, in long-term inconvenience. However, because these systems recognize a relatively large number of discrete environmental conditions, they must be taught a correspondingly large number of predetermined shading settings, causing substantial short-term inconvenience. This may be an unacceptable trade-off for some users.
Sensor-Based Continuous Control Systems
A sensor-based continuous control system automatically adjusts the shading across a continuous range of settings, in response to the output of one or more sensors, to maintain a desired condition (e.g., a desired interior brightness level). Such systems can be either open-loop or closed-loop:                In an open-loop system, the sensed variable is not affected by the shading setting. For example, an open-loop daylight-control system might sense the daylight level outside a building, and then adjust the shading to maintain a near-constant estimated (versus measured) level of daylight inside the building.        An example of such an open-loop system is the photosensitive automatic blind controller disclosed in U.S. Pat. No. 5,532,560 to Element et al (1996). This system includes an outward facing light sensor, mounted on the outward-facing side of a motorized Venetian blind, to sense the daylight level incident on the blind. The controller automatically adjusts the blind to provide a degree of shading that depends on the output of the light sensor (as well as a user-generated reference level). Note that Element at al use non-standard definitions of the terms “open loop” and “closed loop”: they use the term “open loop” to refer to discrete control systems, and the term “closed loop” to refer to continuous control systems; thus, because their system provides continuous control, they deem it a “closed loop” system. However, according to conventional practice (and for purposes of this disclosure), their system is actually an open-loop system, because the sensed variable (i.e. the exterior daylight level) is not affected by the setting of the blind.        In a closed-loop system, the sensed variable is directly affected by the shading setting, and the system adjusts the shading to reduce the difference between the measured and desired values of the sensed variable. For example, a closed-loop daylight control system might sense the daylight level inside the window—and then adjust the shading to maintain that level at some desired value.        One of the earliest such closed-loop systems is the automated window screen disclosed in U.S. Pat. No. 3,294,152 to Kuijvenhoven (1966). Kuijvenhoven shows a roller-type window shade, driven by a reversible electric motor, actuated in response to the light level measured by an inward-facing photoconductive cell mounted within a room. The shade is raised or lowered to maintain an approximately constant, user-specified level of daylight, as sensed by the photoconductive cell.        
An advantage of sensor-based continuous-control systems is that they do not require “teaching” of predetermined shading settings (other than to define the bounds of the allowable shading range). Instead, these systems are equipped with input means to enable the user to specify a “set point” that defines the condition to be maintained (e.g. a desired level of daylight, analogous to the temperature set-point in a thermostat). The system—not the user—then determines the required shading setting to maintain the desired condition.
FIG. 4: Inconvenience Associated with Sensor-Based Continuous Control System
FIG. 4 shows a plot of estimated inconvenience versus time for a sensor-based continuous-control automated shading system. This system requires no programming, so that it does not incur significant short-term inconvenience.
However, users typically do not want a particular shading-determined condition—e.g., a desired level of daylight—to be maintained indefinitely. Rather, users typically prefer different shading-determined conditions at different times. For example, a user might desire a constant level of daylight during work hours, but prefer full shading (for privacy) at nighttime. Pure continuous control systems, as described above, cannot anticipate such changing preferences. Thus, sensor-based continuous-control systems do not substantially reduce the long-term inconvenience associated with deliberate shading adjustments.
Clock-Based Systems
A clock-based system adjusts the shading to predetermined settings at predetermined times (and, optionally, on predetermined days). Each such shading “event” must be taught to the system before use. This typically entails entering the time and shading setting for each desired shading event, via a keypad, in a process similar to that used in programming alarm clocks or early Video-Cassette Recorders (VCR's).
Examples of such systems include the automated shading systems manufactured by Somfy Systems of Cranbury, N.J., that include that the optional Chronis RTS Timer.
FIG. 5: Inconvenience Associated with Clock-Based System
FIG. 5 shows a plot of estimated inconvenience versus time for a clock-based automated shading system.
Such systems are most effective in buildings in which the occupants adhere to a rigid schedule, such as schools.
FIG. 5 assumes such a building.
However, even in such buildings, clock-based systems suffer from the disadvantage that they cannot automatically adapt to changing conditions, such as changes in the weather or in the occupants' activities. Thus, while such systems can provide a noticeable reduction in long-term inconvenience associated with deliberate shading adjustments, they cannot substantially eliminate it. And such systems are even less effective in buildings in which the occupants do not always adhere to a rigid schedule, such as homes.
Further, clock-based systems can provide the level of effectiveness depicted in FIG. 5 only if the user programs a relatively large number of scheduled shading events; as shown in the figure, this results in substantial short-term inconvenience.
Summary of Prior-Art Limitations
As discussed above, prior-art automated shading systems suffer from one or both of two disadvantages:                They are unable to substantially eliminate the long-term inconvenience of deliberate shading adjustments.        They may require an inconvenient and intimidating programming or teaching process, thus causing substantial short-term inconvenience.        